1. Field of the Invention
The present invention relates to a new aromatic polycarbonate resin, an electrophotographic photoconductor containing the aromatic polycarbonate resin, a dihydroxy diphenyl ether compound useful as a raw material monomer of the aromatic polycarbonate resin, and a process of manufacturing the dihydroxy diphenyl ether compound. More specifically, the present invention relates to the aromatic polycarbonate resin having a specific diphenyl ether structure that is useful as a material of the electrophotographic photoconductor; the electrophotographic photoconductor containing the aromatic polycarbonate resin and having high sensitivity and high durability; the dihydroxy diphenyl ether compound useful as the raw material monomer of a high polymer material such as the aromatic polycarbonate resin and the like that is excellent in wear resistance, heat resistance, and the like; and the process of selectively and easily manufacturing the dihydroxy diphenyl ether compound.
2. Description of the Related Art
A typical and known aromatic polycarbonate resin is the one that is obtained by reacting phosgene or diphenyl carbonate with 2,2-bis(4-hydroxy phenyl)propane (for short, hereinafter referred to as “bisphenol A”). The polycarbonate resin obtained from the bisphenol A is excellent in such properties as transparency, heat resistance, dimensional accuracy/precision, mechanical strength, and the like, and thereby is used in many fields. For example, many studies have been done on the bisphenol A as a binder resin for organic photoconductor that is used for electrophotography. A typical constitutional example of the organic photoconductor includes a laminated photoconductor formed by sequentially laminating on a conductive substrate a charge generating layer and a charge transporting layer. The charge transporting layer is formed with a low molecular charge transporting material and a binder resin. As the binder resin, many aromatic polycarbonate resins are named. The above containing of the low molecular charge transporting material, however, may lower the intrinsic mechanical strength of the binder resin, thereby causing such failures of the photoconductor as deteriorated wear resistance, scratches, cracks and the like. With this, the durability of the photoconductor may be lost.
Proposed in the past as a photoconductive high polymer material include vinyl polymers such as polyvinyl anthracene, polyvinyl pyrene, poly-N-vinyl carbazole and the like, although they are not sufficient in terms of photosensitivity. On the other hand, the study is done on a high polymer material having charge transportability, so as to overcome shortcomings of the laminated photoconductor. Examples of the above high polymer material include an acrylic resin having a triphenyl amine structure (M. Stolka et al, J. Polym. Sci., vol 21, 969 (1983)) and a vinyl polymer having a hydrazone structure (Japan Hard Copy '89 P. 67). Moreover the above examples include polycarbonate resin having triaryl amine structure (U.S. Pat. No. 4,801,517, U.S. Pat. No. 4,806,443, U.S. Pat. No. 4,806,444, U.S. Pat. No. 4,937,165, U.S. Pat. No. 4,959,288, U.S. Pat. No. 5,030,532, U.S. Pat. No. 5,034,296 U.S. Pat. No. 5,080,989, Japanese Patent Application Laid-Open No. 64-9964, JP-A No. 3-221522, JP-A No. 2-304456, JP-A No. 4-11627, JP-A No. 4-175337, JP-A No. 4-18371, JP-A No. 4-31404, JP-A No. 4-133065, and the like). Any of the above listed are not practical. Moreover, an aromatic polycarbonate resin having α-phenyl stilbene structure (JP-A No. 11-29634), an aromatic polycarbonate resin having carbazole (Japanese Patent No. 2958100) are studied, but they are not practical.
By using a tetraaryl benzidine derivative as a model compound, M. A. Abkowitz and others made a comparison between a polycarbonate of low dispersion type with a polycarbonate of high polymer, to find that the high polymer polycarbonate has one-digit lower drift mobility (for example, Physical Review B46 6705 (1992)). The cause for the above is yet to be clarified. Making of the high polymer can improve the mechanical strength, although leaving problems in electrical properties including sensitivity, residual potential and the like.
The cause therefor is yet to be clarified. A polymer with its main chain having a skeleton featuring charge transportability (represented by tetraaryl benzidine), especially, a polycarbonate resin may bring about a localized electron, which may be caused by an effect of an electron donation property of electron-attractive carbonyl dioxy group and tertiary amine (substituted with an aryl group on a tetraaryl benzidine skeleton). As a result, a molecular design is supposed to be disadvantageous for hole mobility. The above is supposed to be responsible that the making of the high polymer leaves the problems (i.e., insufficiency) in electrical properties including the sensitivity, the residual potential and the like.
On the other hand, a new trial is being studied, using polyallylene vinylene as disclosed in JP-A No. 10-310635.
On the other hand, examples of diol as a raw material of the high polymer compound include aromatic diols such as bisphenol A, bisphenol S, bisphenol Z, hydroquinone, resorcinol, 4,4′-dihydroxy diphenyl, 2,6-dihydroxy naphthalene, 2,5-dihydroxy naphthalene, and the like; and aliphatic diols and alicyclic diols such as ethylene glycol, propylene glycol, cyclohexane dimethanol, and the like. The above diols are used as constitutional component of resins such as polycarbonate, polyester, polyurethane, polyether, and the like.
Especially, examples of typical known aromatic polycarbonate resin include a polycarbonate resin that is obtained by reacting phosgene or diphenyl carbonate with bisphenol A. The above polycarbonate resin from the bisphenol A is excellent in properties such as transparency, heat resistance, dimensional accuracy/precision, mechanical strength, and the like, and thereby is used in many fields.
For the purpose of improving the heat resistance, chemical resistance, mechanical property of the resins including the polycarbonate, polyester, polyurethane, polyether and the like, introduction of a constitutional component having an ether bond in molecule is known. Examples of the above include 4,4′-dihydroxy diphenyl ether, 4,4′-dihydroxy-3,3′-dimethyl diphenyl ether, and the like.
Processes of manufacturing the dihydroxy diphenyl ether compound generally include a first process of directly manufacturing 4,4′-dihydroxy diphenyl ether by heating hydrogen fluoride together (refer to U.S. Pat. No. 2,739,171); a second process of manufacturing 4,4′-dihydroxy diphenyl ether by subjecting a diphenyl ether as a raw material to acylation, Baeyer-Villiger oxidation, and subsequent hydrolysis (refer to JP-A No. 2002-167348); and the like. Moreover, a third process is reported in which a hydroquinone is reacted in an inactive solvent in the presence of a natural aluminum silicate or a synthesized aluminum silicate, to thereby obtain i) from 2-methyl hydroquinone, a 3-isomer mixture of dimethyl hydroxy diphenyl ether and ii) from 2,6-dimethyl hydroquinone, a 3-isomer mixture of tetramethyl dihydroxy diphenyl ether (refer to JP-A No. 49-55635). Moreover, a fourth process is known in which alkoxy phenol is reacted with halide in the presence of i) alkali metal hydride or carbonate and ii) copper or copper compound, to thereby generate dialkoxy diphenyl ether compound, followed by a dealkylation thereof to thereby manufacture 4,4′-dihydroxy-3,3′-dimethyl diphenyl ether compound (refer to JP-A No. 2002-161062).
As described above, the dihydroxy diphenyl ether compound is synthesized. For obtaining the dihydroxy diphenyl ether compound having a substituent in a specific position of molecule, the above process of manufacturing the dihydroxy diphenyl ether compound from the hydroquinone is problematical, since this process needs refining of the isomer mixtures of several types. The above process of reacting the alkoxy phenol with the halide, followed by the dealkylation may cause high temperature, thus elongating man hour for the dealkylation and the like, which is problematical.